KIM HARRISBERG THE people of Welbedacht in South Africa always knew there was something special about their neighbourhood. In contrast to the towering walls and electric fences seen in more crime-ridden urban areas, residents criss-cross between open and interconnected land on undulating green hills and say crime is less frequent. Eager to identify the key to Welbedacht's harmony, researchers think they have discovered one of the answers - its long-standing ethnic diversity, a finding they hope could serve as a model for areas still scarred by apartheid segregation. "This place can be a good example to the rest of the world;  we…